Cephalexin for Pediatric Insect Bites
Cephalexin is NOT indicated for uncomplicated insect bites in pediatric patients, as these reactions are caused by allergic inflammation rather than bacterial infection and do not require antibiotic therapy. 1
Primary Management of Insect Bites
The initial swelling and erythema following insect stings represents an allergic inflammatory response, not infection:
- Cold compresses reduce local pain and swelling 1
- Oral antihistamines and analgesics address pruritus and pain associated with cutaneous reactions 1
- Prompt oral corticosteroids effectively limit swelling in patients with large local reactions, particularly the extensive swelling that typically occurs within the first 24-48 hours 1
When Antibiotics ARE Indicated
Cephalexin becomes appropriate only when secondary bacterial infection develops, which is uncommon but can occur as a complication:
- Signs of secondary infection include: increasing warmth, purulent drainage, expanding erythema beyond the initial reaction zone, fever, or lymphangitic streaking 1, 2
- For confirmed secondary bacterial cellulitis, cephalexin dosing is 25-50 mg/kg/day divided into 3-4 doses for 5-10 days 3
- This targets β-hemolytic streptococci and methicillin-susceptible Staphylococcus aureus, the typical pathogens in secondary skin infections 1, 3
Critical Clinical Pitfalls
The most common error is prescribing antibiotics for normal inflammatory reactions to insect bites:
- Fire ant stings produce sterile pseudopustules within 24 hours that are caused by necrotic tissue, not infection—leave intact and keep clean 1
- Large local reactions with significant swelling are allergic, not infectious, and resolve with anti-inflammatory treatment rather than antibiotics 1
- Prophylactic antibiotics for uncomplicated bites promote antimicrobial resistance without clinical benefit 1
Alternative Considerations for True Infection
If MRSA is suspected based on purulent drainage or treatment failure:
- Clindamycin 25-40 mg/kg/day divided every 6-8 hours is preferred in regions where local MRSA resistance to clindamycin is <10% 3
- TMP-SMX or other MRSA-active agents should be considered rather than continuing cephalexin 3
- Reassess at 48-72 hours—lack of improvement with β-lactam therapy suggests MRSA or need for alternative coverage 3